1. Field of the Invention
The present invention relates to a light guide plate using back-lighting or front-lighting to illuminate a liquid crystal display (LCD), and particularly to a light guide plate having a bottom surface configured to ensure uniform illumination.
2. The Prior Art
In general, LCDs have two main advantages in comparison with cathode ray tubes (CRTs): LCDs are thin, and have low power consumption. It has been said that LCDs might one day completely replace CRT display devices, and LCDs have aroused great interest in many industries in recent times. In general, an LCD needs a surface light source to provide even light for a clear display.
A surface light source generally comprises a light source and a light guide plate. The light source may be a linear light source, or one or more point light sources. The light guide plate has an end face through which light is introduced, and two opposite major faces one of which functions as an emission face. The performance of the surface light source mainly depends on the characteristics of the light guide plate employed therein.
A light guide plate functions to change a propagation direction of light beams introduced into the light guide plate through a side end face thereof. The propagation direction is changed from a direction roughly parallel to an emission face of the light guide plate to a direction perpendicular to the emission face. A simple, planar transparent light guide plate has poor capability for deflecting light, and provides unsatisfactory brightness at the emission face. Various modifications of the light guide plate have been devised for promoting bright and uniform emission at the emission face.
For example, referring to FIG. 9, a conventional light guide plate 10 includes a light incident surface 101, a light emitting surface 102 adjoining the light incident surface 101, and a bottom surface 103 opposite to the light emitting surface 102. The bottom surface 103 defines a plurality of parallel V-shaped grooves 11, with the V-shaped grooves 11 being oriented parallel to the light incident surface.
As shown in FIG. 10, in use of the light guide plate 10, light beams from a light source (not shown) are introduced into the light guide plate 10 through the light incident surface 101. A portion of the light beams directly propagates out from the light emitting surface 102. Another portion of the light beams propagates to the bottom surface 103, and is reflected by the V-shaped grooves 11 toward the emitting surface 102. The V-shaped grooves 11 can reflect light beams in different directions, and thereby eliminate total internal reflection. The vertex angle of the V-shaped grooves 11 can be configured to control the overall emission of light beams from the light emitting surface 102. However, the V-shaped grooves 11 have a single uniform orientation, such that light beams reflected have only a limited range of directions. Thus, the light guide plate 10 generally does not provide uniform emission over the whole of the light emitting surface 102.
A new light guide plate that overcomes the above-mentioned disadvantages is desired.